Does this gif drive you crazy? Turns out our brains prefer left to right motion, which explains why old side-scrolling games were almost always set up that way. Looking at it feels wrong because we have a “fundamental bias for visual motion”. Even italics lean toward the right, conveying motion in that direction.
“What artistic conventions are used to convey the motion of animate and inanimate items in still images, such as drawings and photographs? One graphic convention involves depicting items leaning forward into their movement, with greater leaning conveying greater speed. Another convention, revealed in the present study, involves depicting items moving from left to right.”
However, this bias does not apply to people or objects which are stationary.
“Whereas a rightward bias is found for photographs of animate and inanimate items in motion (more so the faster is the motion being conveyed), either no bias or a leftward bias is found for the same items in static pose. This could indicate a fundamental left-to-right bias for visual motion.”
So left to right side-scrolling games are backed up by science, but we’ll have to wait for another study to learn why that’s the direction we all prefer.